This invention relates to a device for transferring gobs of molten glass from a supply of gobs to a blank mold of one of a plurality of side-by-side sections of a glass container forming machine of the individual section (I.S.) type. Specifically, this invention relates to a downwardly inclined device of the foregoing character, which is usually referred to as a trough, through which gobs pass in series enroute from an oscillating gob scoop to an I.S. machine section blank mold. The invention also relates to an oscillating gob scoop for transferring gobs of molten glass from a gob shear device to a relatively fixed trough.
Most bottles and jars and other types of glass containers are now formed on an I.S. machine, which typically is made up of a multiplicity of like side-by-side container forming sections, for example eight or ten or even twelve such sections. Further, in higher productivity versions of I.S. machines, a multiplicity of like containers are simultaneously formed at each I.S. machine section, for example, two or three or even four such containers, by processes often described as the double gob process, the triple gob process or the quad process, respectively. In any case, each container formed by an I.S. machine section is formed from a gob of formable, molten glass in a two-step process. In the first of these steps, a preform of the container, which is often described as a blank or a parison, is formed in a first mold, often referred to as a blank mold, by blowing or pressing. The blank or parison, which is formed in an inverted position, that is, with its upper opening positioned beneath its bottom, is then transferred, by a 180xc2x0 turning motion in a vertical plane, to a second mold, usually referred to as the blow mold, where it is blown into its final configuration, while in its normal upright orientation, after which the container along with the other containers simultaneously formed at such I.S. machine section are transferred out of the I.S. machine for further processing.
A delivery system for delivering gobs of molten glass from a gob shear device to an I.S. machine blank mold is made up of an oscillating gob scoop through which the gobs pass enroute to a substantially parallel plurality of pairs of devices that are fixed, though adjustably so, these devices being a straight, downwardly inclined trough that receives gobs from the oscillating gob scoop and a downwardly inclined deflector, which has a downwardly curved portion, that receives gobs from the trough and directs them to an I.S. machine section blank mold. This general arrangement is described in U.S. Pat. No. 4,529,431 (Mumford), which is assigned to a predecessor of the assignee of this application, the disclosure of which is incorporated by reference herein.
Gob delivery troughs of the type described above typically have a cross-section of an upwardly facing U, with the spacing between the legs of the U being determined by the size of the gobs to be passed therethrough. Thus, it has been necessary to replace gob delivery troughs for each I.S. machine section blank mold when it is desired to form containers of a substantially different size from the containers previously formed by such machine, which requires that the size of the gobs being delivered to the machine be increased or decreased accordingly. Heretofore, the replacement of troughs and deflectors has been frequently required for I.S. machines used to produce a wide variety of types and sizes of containers, and each such replacement is labor intensive, and therefore expensive, and time consuming, during which no containers are being produced by the I.S. machine.
It has also been determined that the time required for each gob to travel through a trough on its travel from an oscillating scoop to a blank mold can vary depending on the temperatures of the trough, because the coefficient of friction between the gob and the trough is higher when the temperatures of the trough are higher. This effect is more pronounced in I.S. machines with a relatively large number of sections, for example, ten or twelve sections, because the gob travel distances are longer to the blank molds of the outboard sections of the machine than to the interior sections of the machine. This phenomenon indicates the desirability of positively cooling the troughs and the deflectors of an I.S. machine, or at least those leading to the outboard sections of the machine, but the capital cost of doing so when a plurality of sets of troughs is required for each I.S. machine to accommodate a variety of gob sizes to be processed by the machine is a major deterrent to the use of positive cooling of troughs.
Another problem associated with prior art gob troughs arises from the fact that liquid coolant of the type used to cool shear devices that are used to shear gobs from streams of molten glass tends to flow downwardly through the troughs and tends to undesirably overcool or chill any portion of the gobs that may contact the bottom of the trough as they flow through the trough.
While the problem of variable travel times as a result of variable travel distances is not as serious a problem with oscillating gob scoops as it is with fixed gob troughs, it is still important to be able to reduce the required number of gob scoops per forming machine by increasing the range of gob sizes that can be accommodated by a given gob scoop without compromising the accuracy of the positioning of any gobs in a wide range of sizes with respect to the inlets of the gob troughs into which they are to be delivered.
The aforesaid and other problems associated with prior art glass gob delivery troughs are solved by glass gob delivery troughs according to the present invention. Illustratively, a gob delivery trough according to the present invention has a cross-section of an upwardly facing V. The space between the opposed legs of the V varies from a greater space at the top or open end of the V to a substantially lesser space at the bottom or closed end of the V, the space at the top or upper end of the V being greater than the width of the largest gob to be passed through the trough, and the space at the bottom or closed end of the V being less than the width of the smallest gob to be passed therethrough. This ensures that all gobs over a wide size range can be passed through the trough without the need to replace the trough to accommodate gobs of various sizes within the range, while also ensuring that no gob within the size range will be in contact with the bottom of the trough, and will, therefore, out of contact with any liquid coolant flowing through the trough. Further, a trough according to the present invention can be provided with an underlying air manifold for introducing compressed or fan air into the trough, through openings in the trough, to equalize trough to trough temperatures within the various troughs used on any given I.S. machine, and thereby provide more uniformity in the arrival times of the gobs at the various sections of the I.S. machine, notwithstanding inherent variations in the lengths of the troughs of an I.S. machine. This cooling air, if desired, can also be used to partly levitate the glass gobs in the trough, to speed up the travel of gobs through the trough.
A gob scoop according to the present invention, like the gob trough according to the present invention, has a cross-section of an upwardly facing V with a space between the free ends of its opposed leg being greater than that required for the largest gob to be passed therethrough. Thus, the space between the opposed legs of the V varies from a greater space at the top or open end of the V to a substantially lesser space at the bottom or closed end of the V, the space at the bottom or closed end of the V being less than the width of the smallest gob to be passed therethrough. This ensures that all gobs over a wide size range can be passed through the scoop without the need to replace the scoop to accommodate gobs of various sizes within the range, while also ensuring that no gob within the size range will be in contact with the bottom of the scoop, and will therefore, be out of contact with any liquid coolant flowing through the scoop. Further, a scoop according to the present invention can be provided with an underlying air manifold for introducing compressed or fan air into the scoop, through openings in the scoop, to equalize scoop to scoop temperatures within the various scoops used on any given I.S. machine, and thereby provide more uniformity in the arrival times of the gobs at the troughs leading to the various sections of the I.S. machine. This cooling air, if desired, can also be used to partly levitate the glass gobs in the scoop, to speed up the travel times of gobs through the scoop.
Alternatively, a scoop according to the present invention can be provided with an underlying flow passage for a liquid coolant, such as water, to indirectly cool the gob contacting surface of the scoop to thereby prevent thermal degradation of the material from which the scoop is to be cast or fabricated and to reduce the coefficient of friction between the gobs and the gob contacting surfaces of the scoop. In any case, with proper scoop cooling and with a very smooth gob contacting finish, it is possible to avoid the need to coat the gob contacting surfaces of the scoop to minimize heat transfer from the gobs to the scoop as the gobs travel through the scoop.
Accordingly, it is an object of the present invention to provide an improved trough for conveying gobs of molten glass from an oscillating gob scoop to a blank mold of an I.S. glass forming machine. More particularly, it is an object of the present invention to provide a trough of the foregoing character that is capable of handling a wide range of sizes of gobs, to eliminate the need for frequent replacement of troughs on an I.S. machine when the machine is converted to the manufacture of glass containers of a different size, from glass gobs of a different size. Even more particularly, it is an object of the present invention to provide a trough of the foregoing character that is shaped to ensure that gobs passing therethrough will be maintained out of contact with any liquid coolant that may be flowing through the trough at the bottom thereof.
It is also an object of the present invention, to provide an improved scoop for conveying gobs of molten glass from a gob shearing device to a trough for conveying gobs of molten glass to a blank mold of a I.S. glass forming machine. More particularly, it is an object of the present invention to provide a scoop of the foregoing character that is capable of handling a wide range of sizes of gobs, to eliminate the need for frequent replacement of scoops on a I.S. machine when the machine is converted to the manufacture of glass containers of a different size, from glass gobs of a different size. Even more particularly, it is an object of the present invention to provide a scoop of the foregoing character that is shaped to ensure that gobs passing therethrough will be maintained out of contact with any liquid coolant that may be flowing through the scoop at the bottom thereof.
For a further understanding of the present invention, and the objects thereof, attention is directed to the drawing and the following brief description thereof, to the detailed description of the preferred embodiment and to the appended claims.